实体类转SQL工具类

主要的目标是简化开发人员在有实体类的情况下时做的重复性工作，提高开发效率。

单个实体类的转换工具类

1.EntityToTableConverter工具类

import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Field;
import java.math.BigDecimal;/*** 将实体类转换为MySQL建表语句并输出到文件中的工具类* Author: 木芒果*/
public class EntityToTableConverter {/*** 将实体类转换为MySQL建表语句并输出到文件中** @param clazz    实体类的Class对象* @param filePath 输出文件的路径：如"User.sql",就会在项目根目录下创建一个名为User.sql的文件，文件路径为空则将建表语句输出到控制台* @throws IOException 如果输出文件时发生错误*/public static void convertToCreateTableStatement(Class<?> clazz, String filePath) {try {StringBuilder sb = new StringBuilder();sb.append("DROP TABLE IF EXISTS ");String simpleName = clazz.getSimpleName();sb.append(convertCamelToUnderline(simpleName));sb.append(";\n");sb.append("CREATE TABLE ");sb.append(convertCamelToUnderline(simpleName));sb.append(" (\n");Field[] fields = clazz.getDeclaredFields();for (int i = 0; i < fields.length; i++) {Field field = fields[i];sb.append("    ");String fieldName = field.getName();if (fieldName != "serialVersionUID") {sb.append(convertCamelToUnderline(fieldName));sb.append(" ");sb.append(getColumnType(field.getType()));if (fieldName.equals("id")) { // 如果字段名为"id"，则自动设置为主键，自动增长sb.append(" PRIMARY KEY AUTO_INCREMENT");}sb.append(",\n");}}sb.deleteCharAt(sb.lastIndexOf(","));sb.append(");");if (filePath == null) {System.out.println(sb);return;}FileWriter writer = new FileWriter(filePath);writer.write(sb.toString());writer.close();System.out.println("建表语句已输出到" + filePath);} catch (Exception e) {e.printStackTrace();}}/*** 获取字段类型对应的MySQL数据类型** @param fieldType 字段类型* @return MySQL数据类型*/private static String getColumnType(Class<?> fieldType) {if (fieldType == String.class) {return "VARCHAR(255)";} else if (fieldType == int.class || fieldType == Integer.class) {return "INT";} else if (fieldType == long.class || fieldType == Long.class) {return "BIGINT";} else if (fieldType == double.class || fieldType == Double.class) {return "DOUBLE";} else if (fieldType == boolean.class || fieldType == Boolean.class) {return "BOOLEAN";} else if (fieldType == byte[].class) {return "LONGBLOB";} else if (fieldType == java.util.Date.class || fieldType == java.sql.Timestamp.class || fieldType == java.time.LocalDateTime.class) {return "DATETIME";} else if (fieldType == BigDecimal.class) {return "DECIMAL(10,2)"; // 可根据需要调整精度和小数位数}// 如果遇到无法识别的类型，可以根据实际需求进行扩展return "VARCHAR(255)";}/*** 将驼峰命名法转换为下划线命名法** @param camel 驼峰命名法字符串* @return 下划线命名法字符串*/private static String convertCamelToUnderline(String camel) {StringBuilder sb = new StringBuilder();for (int i = 0; i < camel.length(); i++) {char c = camel.charAt(i);if (Character.isUpperCase(c)) {if (i == 0) {sb.append(Character.toLowerCase(c));} else {sb.append('_');sb.append(Character.toLowerCase(c));}} else {sb.append(c);}}return sb.toString();}
}

2.测试

/*** @author 木芒果*/
public class Test {public static void main(String[] args) {//生成sql文件的方式EntityToTableConverter.convertToCreateTableStatement(User.class, "user.sql");//直接输出在控制台的方式EntityToTableConverter.convertToCreateTableStatement(User.class, null);}
}

整个包中的实体类转换工具类

1.EntityToTableConverter工具类

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;/*** 将整个包下的实体类转换为MySQL建表语句* Author: 木芒果*/
public class EntityToTableConverter {/*** 将指定包下的所有实体类转换为MySQL建表语句并输出到文件中** @param packageName 包名* @param filePath    输出文件的路径* @throws IOException 如果输出文件时发生错误*/public static void convertEntitesToCreateTableStatements(String packageName, String filePath) {try {Set<Class<?>> classes = getClassesInPackage(packageName);StringBuilder sb = new StringBuilder();for (Class<?> clazz : classes) {sb.append(convertToCreateTableStatement(clazz));sb.append("\n\n");}if (filePath == null || filePath.isEmpty()) {System.out.println(sb);return;}FileWriter writer = new FileWriter(filePath);writer.write(sb.toString());writer.close();System.out.println("建表语句已输出到" + filePath);} catch (Exception e) {e.printStackTrace();}}/*** 获取指定包下的所有类** @param packageName 包名* @return 类集合*/private static Set<Class<?>> getClassesInPackage(String packageName) {try {Set<Class<?>> classes = new HashSet<>();String packagePath = packageName.replace(".", "/");ClassLoader classLoader = Thread.currentThread().getContextClassLoader();Enumeration<URL> resources = classLoader.getResources(packagePath);while (resources.hasMoreElements()) {URL resource = resources.nextElement();if (resource.getProtocol().equals("jar")) {JarURLConnection jarConnection = (JarURLConnection) resource.openConnection();JarFile jarFile = jarConnection.getJarFile();for (Enumeration<JarEntry> entries = jarFile.entries(); entries.hasMoreElements(); ) {JarEntry entry = entries.nextElement();String entryName = entry.getName();if (entryName.startsWith(packagePath) && entryName.endsWith(".class")) {String className = entryName.substring(0, entryName.length() - 6).replace("/", ".");Class<?> clazz = Class.forName(className);classes.add(clazz);}}} else if (resource.getProtocol().equals("file")) {File packageDir = new File(resource.getFile());if (packageDir.exists()) {File[] files = packageDir.listFiles();for (File file : files) {String fileName = file.getName();String className;if (fileName.endsWith(".class")) {className = packageName + "." + fileName.substring(0, fileName.length() - 6);Class<?> clazz = Class.forName(className);classes.add(clazz);} else if (file.isDirectory()) {String subPackageName = packageName + "." + fileName;classes.addAll(getClassesInPackage(subPackageName));}}}}}return classes;} catch (Exception e) {e.printStackTrace();return null;}}/*** 将实体类转换为MySQL建表语句** @param clazz 实体类的Class对象* @return 建表语句*/private static String convertToCreateTableStatement(Class<?> clazz) {StringBuilder sb = new StringBuilder();sb.append("DROP TABLE IF EXISTS ");String simpleName = clazz.getSimpleName();sb.append(convertCamelToUnderline(simpleName));sb.append(";\n");sb.append("CREATE TABLE ");sb.append(convertCamelToUnderline(simpleName));sb.append(" (\n");Field[] fields = clazz.getDeclaredFields();for (int i = 0; i < fields.length; i++) {Field field = fields[i];sb.append("    ");String fieldName = field.getName();if (fieldName != "serialVersionUID") {sb.append(convertCamelToUnderline(fieldName));sb.append(" ");sb.append(getColumnType(field.getType()));if (fieldName.equals("id")) { // 如果字段名为"id"，则自动设置为主键，自动增长sb.append(" PRIMARY KEY AUTO_INCREMENT");}sb.append(",\n");}}sb.deleteCharAt(sb.lastIndexOf(","));sb.append("\n);");return sb.toString();}/*** 获取字段类型对应的MySQL数据类型** @param fieldType 字段类型* @return MySQL数据类型*/private static String getColumnType(Class<?> fieldType) {if (fieldType == String.class) {return "VARCHAR(255)";} else if (fieldType == int.class || fieldType == Integer.class) {return "INT";} else if (fieldType == long.class || fieldType == Long.class) {return "BIGINT";} else if (fieldType == double.class || fieldType == Double.class) {return "DOUBLE";} else if (fieldType == boolean.class || fieldType == Boolean.class) {return "BOOLEAN";} else if (fieldType == byte[].class) {return "LONGBLOB";} else if (fieldType == java.util.Date.class || fieldType == java.sql.Timestamp.class || fieldType == java.time.LocalDateTime.class) {return "DATETIME";} else if (fieldType == BigDecimal.class) {return "DECIMAL(10,2)"; // 可根据需要调整精度和小数位数}// 如果遇到无法识别的类型，可以根据实际需求进行扩展return "VARCHAR(255)";}/*** 将驼峰命名法转换为下划线命名法** @param camel 驼峰命名法字符串* @return 下划线命名法字符串*/private static String convertCamelToUnderline(String camel) {StringBuilder sb = new StringBuilder();for (int i = 0; i < camel.length(); i++) {char c = camel.charAt(i);if (Character.isUpperCase(c)) {if (i == 0) {sb.append(Character.toLowerCase(c));} else {sb.append('_');sb.append(Character.toLowerCase(c));}} else {sb.append(c);}}return sb.toString();}
}

2.测试

public class Test {public static void main(String[] args) {//生成sql文件的方式EntityToTableConverter.convertEntitesToCreateTableStatements("com.mmg.entity", "D:\\test.sql");//直接输出在控制台的方式EntityToTableConverter.convertEntitesToCreateTableStatements("com.mmg.entity", null);}
}

如有更好的想法，可以在评论区交流，完善此工具类！